In the past, mattress construction concentrated on the innerspring construction to support the user's lumbar region such as, for example, by varying spring tensions, and material gauge. U.S. Pat. No. 5,325,553 to Ripley et al. provided more attention to the mattress, specifically a spring structure providing support with a continuous frame that encircled coil springs over a major expanse of the central area of the mattress that usually receives and supports the lumbar region of the user's back. While the problem of lumbar support has been partially solved by the mattress structure of Ripley et al., there remains the particular problem of the mattress springs on either side of the traverse frame bars depressing lower than the said bars when the user is received thereon, whereby creating undesired upward pressure into the user's back. This has been a particular problem that prior art mattress structures have attempted to address.
In particular, the mattress structures disclosed by U.S. Pat. No. 2,383,157 to Pink and U.S. Pat. No. 2,131,071 to Radnus both amplify the firmness of certain surface areas of a mattress spring structure by using metallic strips/wire to frame two separate reinforced areas per mattress.
U.S. Pat. No. 3,242,505 to Tyhanic discloses a mattress structure that uses multiple flat bands that traverse the mattress covering the center of the spring coils. The flat bands are connected to an encircling wire frame thereby creating a more uniform horizontal depression of the mattress structure when the user is received on said mattress.
The mattress structures disclosed by U.S. Pat. No. 4,122,566 to Yates and U.S. Pat. No. 5,570,484 to Ogle create two bordered areas of coil springs per mattress spring structure surface, four total, thereby increasing firmness over specific areas of said mattress.
The mattress structure disclosed by U.S. Pat. No. 4,180,877 to Higgins increases mattress spring structure firmness in selected areas using a welded wire grid structure attached to the opposite sides of said mattress.
U.S. Pat. No. 4,348,014 to Litkewycz discloses a mattress structure that increases the firmness of a bedding unit through the use of an auxiliary panel that has a wire border and a plurality of torsion bar springs extending between opposites portions of the peripheral wire and are connect to said wire thereby creating cooperation between coil springs when depressed.
The mattress structure disclosed by U.S. Pat. No. 4,369,534 to Wright increases the firmness of a pre-selected center area of a mattress spring assembly using a grid structure attached to the opposite sides of the mattress. The grid structure is comprised of plastic straps extending diametrically across the mattress in the center third area and overlaid by a preformed wire grid. The plastic straps and wire grid are attached to pre-assembled spring core by conventional connectors such as metal clips and/or hog rings.
U.S. Pat. No. 5,027,459 to Perry, Jr. et al. discloses a mattress structure that creates surface lift through “trampoline” grids on each horizontal plane of the mattress that are connected to the mattress perimeter by a band apparatus.
While the above mentioned prior art mattress structures provide a degree of added support and firmness to certain surface areas of mattress spring structures, they do so with the inefficient use of materials and overly complicated designs. The costs of materials and manufacturing are not taken into account by the prior designs. The complicated structures make it difficult to construct and increase the time to manufacture, thus raising the manpower cost per mattress and lowering the volume of output. Not only do the excessive amounts of material add to the complicated manufacturing process, they also increase the material cost per mattress.
Therefore, what is need is a mattress structure with an improved lumbar zone that does not create an undesired upward pressure into the back of a user's when received thereon, and which can be economically provided.